This invention relates to a variable resistance attenuator for radio frequency power, and more particularly to an attenuator using PIN diodes with adjustable direct-current bias connected to two ports of a hybrid.
Various variable resistance attenuators are known which make use of the property of PIN diodes that the RF resistance is a function of the direct-current bias. These include PI and bridged T configurations. It is also known to use two PIN diodes connected back-to-back across two ports of a 3 dB, quadrature hybrid, with adjustable DC bias. See for example Hewlett Packard Application Note 922, page 10.
There are also known modulator and mixer circuits which use four matched diodes in a bridge configuration.